Do you know in new standard of HTML5 there is no support for flash.To fulfill this requirement Html5 has some of the new elements.With use of these elements embedding of video, audio and animated images become more easier. Even Apple does not support flash in its device so if you are thinking of having website with flash which also get supported in Iphone and Ipad, use html5.
All I know is people are using HTML 5 to make the flash video information be crawled by SE bots resulting to that video will be visible in search engine result page when the matching keyword used.